My experiments using the tilt sensors to fly a spaceship model have turned into a 2D Asteroids-like game with 3D models. The tilt sensor has been replaced with standard virtual joystick controls for the iPhone.
This started off as a simple shooter but quickly started to take on a story-line; I have about 20 missions planned, focusing on a war between Asteroid Belt colonists and a Mars/Earth alliance.
Spaceship models were bought from the excellent 3drt.com
You can try out a playable web demo here (4 missions written so far)